bug#59935: 29.0.60; project-list-buffers is slow

[Dmitry Gutov <dgutov@yandex.ru>]

On 11/12/2022 12:54, Eli Zaretskii wrote:
>> Date: Sun, 11 Dec 2022 12:23:13 +0200
>> Cc: 59935@debbugs.gnu.org, juri@linkov.net
>> From: Dmitry Gutov <dgutov@yandex.ru>
>>
>> The main problematic behavior (low performance) is exhibited by the
>> "latest" branch, which looks like this:
>>
>>     (let ((pr (project-current t)))
>>         (display-buffer
>>          (if (version< emacs-version "29.0.50")
>>              ;; ...
>>            (list-buffers-noselect
>>             arg nil (lambda (buf) (memq buf (project-buffers pr)))))))
> 
> Yes, I see that.  I still don't understand: this can easily be changed
> to call project-buffers just once.

Cue my very first response:

   If we just do that, pressing 'g' will only show the buffers that
   belonged to the project when project-list-buffers was called. And not
   necessarily the *current* list of project buffers.

Though I guess there might be ways to avoid this, like creating a cache 
which will be invalidated in post-command-hook, something like that.

>>> Anyway, I only entered this discussion because you asked about making
>>> some non-trivial changes on the release branch.  If that is no longer
>>> an issue, I will gladly bow out of this.
>>
>> I expect Juri is going to argue for that later. For non-trivial changes
>> in buff-menu.el, no less.
> 
> I will wait for his comments, then.

Let's.